Hindsight Informs Foresight: Revisiting Millennial Forecasts of Impacts and Status of Rocky Shores in 2025.

Rocky shorelines are characterised by vulnerability to both land- and sea-derived impacts. They face acute impacts such as pollution from shipping accidents, chronic pollution from point sources, run-off and catchments plus disturbances by food gathering, recreation and sediment deposition in sheltered areas. Coastal urbanisation can both impact natural shores and create impoverished artificial rocky shores. Superimposed upon local and regional scale impacts are global environmental changes including warming, sea-level rise, increasing storm frequency, ocean acidification and non-native invasive species. Rocky shores are, however, amenable to long-term ecological monitoring and ecological experimentation. Thompson, Crowe and Hawkins (2002) reviewed anthropogenic impacts on rocky intertidal habitats and forecasted their status for the next 25 years. The paper was critiqued by invited experts (Branch, Castilla) at a subsequent conference in 2003 (Environmental Future of Aquatic Ecosystems, Zurich, 23-27 March 2003), culminating in a consensus chapter in Aquatic Ecosystems: Trends and Global Prospects (Branch et al., 2008). Nearly 25 years later, we revisit and evaluate their predictions to explore implications for the next 25 years as new potential impacts emerge in parallel with societal attempts to transition to net zero carbon outputs. An update is provided on what was largely correct (oil-spills, food harvest, invasive species, sedimentation/run-off, organotins, global-change, artificial habitats, recreation/research/education) and what was partially/completely wrong (eutrophication, aquaculture/GMOs, renewable energy, UV radiation) or omitted (coastal mining, ocean acidification, plastic, light, noise pollution). We also consider the challenges and uncertainties inherent in predicting impacts of environmental changes by using hindsight to inform foresight.